Process of making nylon fabrics elastic by treatment with formaldehyde



Patented May 4, 1948 PROCESS OF ALDE E Allan K. Schneider, Wilmington,

to E. I. du Pont de Nemours &

Del, a corporation of Delaware mington,

G NYLON FABRICS MAKIN ELASTIC BY TREATMENT WITH FORM- Del., assignorCompany, Wil- No Drawing. Application February 20, 1945, Serial No.578,945

11 Claims.

This invention relates to textile fabrics, and more particularly toelastic fabrics and methods for their preparation.

Elastic fabrics constructed from covered rubber monofils and cut rubberstrips are well known. These fabrics, which may have a one-way or twowaystretch depending upon the construction are usually heavy and stiff.This results from the inability to spin a fine denier rubber thread andthe need for a relatively heavy covering of a nonelastic wrapper toprovide strength, a dyeable surface, and a more pleasant feel. Thisspecial fabric, moreover, is expensive to produce clue to the cost ofwrapping the individual strips, the diificulty of weaving and to thecomplicated machinery involved.

Valuable elastic fabrics can also be obtained from yarns spun from amodified nylon known as N -alkoxymethyl polyamide. The N-alkoxymethylpolyamide is made by reacting the initial nylon thigh molecular weightor fiber-forming synthetic linear polyamides of the kind described inPatents 2,071,250, 2,071,253 and 2,130,948) with alcohol, formaldehydeand acid catalyst. The yarns of N-alkoxymethyl polyamide have a finedenier with exceptional elasticity, and can be woven or knit into highlyelastic fabrics without the need for a heavy nonelastic wrapping on thefibers. The manufacture of such fabrics, however, involves thedifficulties incident to weaving elastic yarns, and the weaving must becontrolled by special procedures in the same manner as with coveredrubber fibers.

This invention has as an object a method for obtaining elastic fabricsof the kind just mentioned and from similar polyamide material, butwithout either wrapping or weaving of an elastic material. A furtherobject is the manufacture of fabrics having a one way or two way stretchby a method wherein a fabric is prepared from inelastic fiber and thefabric then rendered elastic by a simple after-treatment. Other objectswill appear hereinafter.

The above objects are accomplished by a method which comprises preparinga fabric with a substantial proportion of filaments which are composedof the synthetic linear polyamides described in said patents but whichare undrawn or but partially drawn (and hence unoriented molecularlyalong the filament axis or oriented to but a minor degree), and thentreating the fabric with a reaction mixture which comprises alcohol,formaldehyde, and an acid catalyst, and which produces an elastic fabricthrough the reaction of said composition with the undrawn filaments 2 toform N-alkoxymethyl polyamide in substantial amount.

The accomplishment of the objects of this invention through the reactioninvolved in the formation of N-alkoxymethyl groups upon a substantialnumber of the amide groups in the undrawn (1. e., unoriented) portion ofthe polyamide fabric, is based upon my observation that whereas thedrawn polyamide fiber, which contains well ordered oriented hydrogenbonded polyamide chains, is essentially unaffected by the abovementioned reaction mixture, the undrawn fiber containing polyamidechains in a disordered grouping readily react with the formaldehyde andalcohol. By this means elasticity is produced within a fabric woven fromnonelastic fibers, and the problems of windup, sizes, twisting andplying, which are involved in spinning elastic yarns, is avoided bycarrying out all the handling and weaving steps on a nonelastic yarn,and then contributing elasticity as a. final step after preparation ofthe fabric.

The undrawn filaments in the filling (or warp) can be converted to anelastic state without sensibly affecting the drawn fibers in the warp(or filling) which serve to maintain the form and strength of the fabricduring the treatment, thus permitting a successful handling of thefabric. Instead of using drawn nylon as the nonreactive fibers in thewarp or filling it is possible to use various other nonreactive fibers,for instance, cotton, rayon, silk, wool or linen in either the warp orfilling. The fabric treated to give the elastic properties should have apreponderant amount, e. g., of undrawn nylon in at least one of eitherthe warp or filling. A two way stretch fabric can be obtained byapplying the present process to a fabric in which undrawn nylon is usedin both the filling and warp. More care, however, must be taken inhandling and control since there is no supporting material to helpmaintain strength and form during the treatment,

It is to be observed that synthetic linear polyamide or nylon filamentsare inherently capable of being cold drawn, that is drawn in the solidstate under tension, to a permanent elongation up to 600% or more oftheir initial length. The undrawn polyamide filaments used in thepractice Of this invention includes those which are drawn, and henceoriented, in minor amount of the above mentioned elongation possible.More particularly, the filaments can be used which have not been drawnmore than 2:1 or 200%, since the reaction still takes place althoughslowly.

In other words, the filaments, if they have been subjected to thisdegree of cold drawing, will be capable of being cold drawn to theresidual amount of at least 300%. This invention, however, is mostadvantageously practiced with nylon filaments which are essentiallywholly undrawn, that is not drawn more than about one-sixth of the totalamount possible, that is with filaments that have not been drawn morethan about 100%.

The fabric prepared from the undrawn polyamide fibers as described aboveis, in the best embodiment of the invention, reacted with the alcoholformaldehyde and acid catalyst at temperatures of from 60 C. to 80 0.,although temperatures from about 50 C. to 90 C. can be used. Theproportion and concentration of the reactants, referred to moreparticularly hereinafter, can vary considerably, and the time willdepend on the temperature, concentration of the acid catalyst, and onseveral other factors. In general the reaction is continued until therehas been some swelling of the undrawn filaments and is discontinuedbefore there is any substantial solution of the filaments in thereaction liquid which would weaken the ultimate fibers or mat themtogether. An excessive period of reaction causes solution of the polymerin the treating bath with a resultant loss of material weight andeventually complete disintegration of the filling and disappearance ofthe fabric structure. The amount of N-alkoxymethyl substitution, whichis the replacement of hydrogen of the amide groups -CONH- in the initialpolyamide with the group CH20R wherein R is an alcohol radical, is atleast 20%, and is preferably 35%-55%. In other words in the polyamidecomposing the undrawn filaments after the alcohol and formaldehydetreatment, hydrogen bearing amide groups consisting of at least 20% ofthe total amide groups have been converted into N-alkoxymethyl groups.

The point of optimum reaction can be readily recognized as the point ofmaximum swelling of the reactant fiber. The swelling occurslongitudinally and laterally and it is more easily recognized as theformer so that when the fabric reaches its greatest extent it is removedfrom the treating solution and quenched to stop the reaction. Thequenching is best carried out in several steps. The swollen fabric isinitially placed in an alcohol, preferably the alcohol employed in thereaction, although ethanol or methanol are satisfactory for universaluse. After the reagents have been partially leached from the fabric thequenching may he stepped down towards a pure water wash in one or twosteps, largely dependent upon the extent of the reaction. Duringquenching the swollen fabrics retract to, or slightly below, theiroriginal length. A direct quench in water tends to cause unevenretraction and to produce a rough sticky surface on the fiber due toprecipitation of a small amount of dissolved N-alkoxymethyl polyamide.

The following procedure is representative of the most desirable andusually used practice of the invention:

Fabric woven from a combination of drawn and undrawn polyhexamethyleneadipamide in the warp and filling, respectively, is immersed in a bathconsisting of methanol, formaldehyde, and an acid catalyst in a ratio ofapproximately :521, and maintained at a temperature of 60-70 C. Aftersome -75 minutes dependent upon the temperature and constitution of thebath, the fabric is removed and quenched in a wash solution. Thecompletely quenched fabric is found to have excellent elasticity in thedirection of the filling, and to be unaffected in the direction of thewarp.

The practice of this invention is illustrated in more detail in thefollowing examples in which the amounts are expressed as parts byweight.

Example I A plain weave fabric woven on a standard ribbon loom with 47filling ends/inch of 480 denier, 13 filament undrawn polyhexamethylencadipamide and warp ends/inch of 102 denier, 13 filamentpolyhexamethylene adipamide, cold drawn to a ratio of 5.221 was placedin a solution consisting of 5 parts methanol, 5 parts paraformaldehyde,and one part anhydrous oxalic acid. The solution was maintained at 65 C.for 20 minutes, at the end of which time the fabric was carefullyremoved, washed in methanol for 10 minutes, then in a 50:50 methanolwater solution, and finally in water for 24 hours. The resulting fabricwas slightly smaller in dimensions than originally, but otherwise hadthe same appearance. However, in the direction of the undrawn fiber thematerial was highly elastic and could be stretched to as high aselongation with a 96% recovery within one minute of relaxation. Therewas no elasticity in the direction of the drawn fiber.

Example 11 A plain weave fabric was constructed from 175 denier cottonwith 60 warp ends/inch and 143 denier, l3 filament undrawn nylon with 50filling ends/inch. The fabric was immersed in a large excess of solutionof 5 parts methanol, 5 parts paraformaldehyde, and 1 part anhydrousoxalic acid at 62-64 C. for 30 minutes. At the end of this period thefabric had extended approximately 100% in width. It was removed andplaced successively in methanol, 9. mixture of equal partsmethanol-water, and in water. The fabric had now shrunk to roughly 75%of its initial width but had the same warp length as originally. Thefabric was highly elastic, stretching to as high as 200% its originalwidth with greater than a 95% recovery of this stretch after relaxation.Examination of the individual fibers revealed that the cotton wasunaffected while the nylon "was soft and pliable and highly elastic. Infact, the separated nylon fibers could be stretched as high as 400% withrecovery of 95% of the stretch on relaxation.

Example III A plain weave fabric was prepared from undrawnpolyhexamethylene adipamide of intrinsic viscosity of 0.9 (intrinsicviscosity defined as in United States Patent 2,130,948). The fabric wasconstructed from denier, i3 filament yarn with 100 warp ends and 50filling ends per inch. A portion of fabric was placed in an excess ofsolution containing 5 parts methanol, 5 parts paraformaldehyde, and 1part oxalic acid dihydrate maintained at a temperature of 65 C. At theend of 40 minutes, the fabric was removed from the solution and waswashed in water. The material was found to be slightly shrunk in size,pliable and soft. It was highly elastic, recovering completely andrapidly from a elongation in the direction of both the warp and thefilling. The cloth before treatment was stiff and harsh, and had noreversible elongation. The

. stretching modulus .of the treated fabric was much lower than that ofthe untreated fabric.

The polyamides which compose the undrawn filaments which are formed intothe fabrics treated by the present process contain hydrogenbearing amidegroups and are, as has been mentioned above. those of the general typedescribed in the patents previously referred to. They are high molecularweight or fiber-forming polymers characterized by an intrinsic viscosityof at least 0.4 as defined in Patent 2,130,948. The polyamides of thiskind comprise the reaction product of a linear polymer-formingcomposition containing amide-forming groups, and can be obtained byseveral methods including polymerization of a monoaminomonocarboxylicacid, by reacting a dlamlne with a dibasic carboxylic acid insubstantially equimolecuiar amounts, or by reaction of amonoaminomonohydric alcohol with a dibasic carboxylic acid insubstantially equimolecular amounts, it being understood that referenceherein to the amino acids, diamines and dibasic carboxylic acids andamino alcohols is intended to include the equivalent amide-formingderivatives of these reactants. On hydrolysis with hydrochloric acid theamino acid polymers yield the amino acid hydrochloride, and thediamine-dibasic acid polymers yield the diamine hydrochloride and thedibasic carboxylic acid, and the amino aicohol-dibasic acid polymersyield the amino alcohol hydrochloride and the dibasic carboxylic acid.The preferred polyamides obtained from these reactants have a unitlength of at least "I, where "unit length is defined as in Patents2,071,253 and 2,130,948. The preferred polyamides of this kind used inthe practice of the present invention are those in which the averagenumber of carbon atoms separating the amide groups is at least two.

Examples of particular reactants that can be used in preparing thepolyamides comprise dibasic carboxylic acids such as glutaric, adipic,pimelic, suberic, azelaic, sebacic, diglycolic, phthalic, terephthalic,isophthalic and p-phenylene diacetic acids; diamines, such asethylenediamine, tetramethylenediamine, pentamethylene diamine,hexamethylene diamine, m-phenylene diamine. p-xylylene diamine, andtrigwcol diamine; and primary monoaminomonocarboxylic acids such asd-aminocaproic and 12- aminostearic. Interpoiyamides can be used in thepractice of this invention. that is, those obtained from a mixture ofpolyarnide-forming compositions. The polyamides previously indicatedinclude also polymers obtained by reaction of a polyamide-formingcomposition with another polymer-forming composition such aspolyesterforming composition. Polyamides that are operable in additionto those already defined are the fiber forming polyureas, e. g.,polydecamethylene urea; polysulfonamides, e. g., the polysulfonamideprepared from decamethylene diamine and m-benzenedisulfonyl chloride;polyurethanes, polythiourethanes, and polyhydrazldes.

With further reference to the reactants used in treating the fabricscontaining the undrawn polyamide, namely, acid catalyst, alcohol, andformaldehyde, the acid catalysts are oxygen-containing acids whichproduce a pH below 3 in the alcohol-formaldehyde solution used and havean equivalent conductance, measured at 25 C. in 0.01 N concentration inwater, no greater than 370 ohms- 0.111.. Buch acids do not causeexcessive degradation of the polyamide. Oxalic acid in a 5% to solutionis particularly suitable. The organic acids which inmethanolformaldehyde solution produce a pH below 3 are preferred. oxalicare m'aleic, fumaric, and the mono-. di-. or trichloroacetic acids, andp-toluenesulfonic acids. Certain inorganic acids and salts, such asphosphoric acid. ammonium bromide and calcium chloride can also be used,but greater care and operation within quite narrow limits is necessaryto prevent excessive solution or degradation of the polymer. The usefulacids are as strong as trimetllylactic acid and not stronger thanp-toluenesulfonic acid.

Although quantities as low as 3% and up to 20% can be used, the mostdesirable amount of catalyst in the reaction solution is, under mostconditions, from 5% to 10% from the standpoint of readily avoiding anundesired degree of solubilization through excess of the catalyst andtoo slow a reaction through an insufficient amount.

Any primary or secondary aliphatic alcohol miscible with theformaldehyde used, for example those dissolving 20% or more ofparaformaldehyde, can be used in the practice of this invention. Thelower alcohols of four carbon atoms or less are the most advantageousfor the present purpose because they produce the greatest dezree ofelasticity in the final product, and also react the most rapidly.Examples of suitable alcohols other than methanol are ethyl, isopropyl,n-propyl, normal, isoand secondary butyl alcohols which may be employedas well as unsaturated alcohols such as allyl, methallyl and crotyl.Benzyl alcohol, ethylene glycol, diethylene glycol, eyclohexyl alcohol,and glycerol are also useful.

The formaldehyde is preferably used as paraformaldehyde, although otherforms of formaldehyde and formaldehyde-liberating substances such aspolyoxymethylene can be used. Aqueous solutions, however, are notdesirable since the presence of water inhibits the reaction. For thisreason the reaction mixture should not contain more than 20% water. Itis preferred to use reaction solutions which are essentially nonaqueous,namely those containing not more than 5% water.

The quantity of formaldehyde and alcohol present in the reaction mixturecan vary over relatively wide limits. The alcohol can be present inamount of from 20% to 75% of the reaction mixture, these amounts beingfrom 30% to 50% for optimum reaction. The reaction mixture can containas high as 75% or as low as 15% formaldehyde although for optimumreaction there should be from 20-40% formaldehyde present, which amountmay be determined by titration with sodium sulflte, following thereaction:

The procedure followed to obtain the most advantageous properties varieswith a number of factors. Thus the use of a high acid concentrationenables more rapid reaction and the use of lower temperatures than doesa low acid concentration. A similar eilect results from a highformaldehyde content. The time required is dependent upon the nature andquantity of the acid and formaldehyde, the temperature, age of thereaction solution, degree of orientation of the fiber, thickness of thefiber, and the constitution of the polyamide. In general, with the bestbalance of conditions between 5 and 60 minutes is the most suitablereaction period. However. at high temperatures and high acid concentra-Examples of these in addition to tions the required elasticity can beobtained within a minute's time while under certain circumstances aslong as hours is necessary.

A modification of this process comprises the application of the aboveprocedure to a polyamide f abrlc in which the synthetic linear polyamidehas previously been subjected to a cross-linking treatment in theundrawn state. This cross-linking can be carried out by reaction of thepolyamide with formaldehyde and an acid catalyst under mild conditionswhich do not give rise to elastic fibers. The cross-linked polyamide isobtained by a baking treatment. Fabric containing such cross-linkedpolyamide has greater resistance to the effect of organic solvents whensubsequently treated with formaldehyde, alcohol and an acid catalyst togive an elastic fabric.

The fabric used in the treatment described herein can have a variety offorms. The essential feature for a one-way stretch is an undrawnunoriented reactive polyamide fiber woven together with a nonreactivefiber such that production of elasticity in the reactive fiber permitselongation of the fabric as a whole. Thus, not only a plain weave, but atwill, satin, figure, double or gauze weave may be employed. In additionto the use of drawn, oriented nylon in the non-reactive direction of theweave. it is possible and often desirable to use other such nonreactivefibers as cotton, mercerized cotton, rayon, linen, silk, wool and caseinfiber. All these fibers are essentially unaffected by the treatmentinvolved. It is, of course, not essential that the undrawn nylon be inthe filling and the drawn nylon in the warp, for the reverse is equallyoperable. However, in weaving it is generally most desirable to employthe drawn yarn in the warp.

The production of a two-way elastic fabric by use of undrawn nylonthroughout is particularly attractive. The procedure is the same as forone-way stretch, although, as has been previously noted, somewhat morecare is required in the handling of the material during reaction. Notonly woven, but also knitted fabric can then be used.

The N-alkoxymethyl polyamide fibers that are formed during the treatmentof the fabric with the reaction solution, and which constitute theelastic portion of the fabric are cross-linked in the process offormation, so that after isolation they are insoluble in alcohols andare essentially infusible. It is possible to obtain further crosslinkingby means of certain aftertreatments. The fabric may be impregnated witha small amount of acid and then baked. For this purpose any organic orinorganic acid, such as maleic. oxalic, sulfuric, hydrochloric, havingan ionization constant greater than 10'", can be used. Again,unsaturated alcohols may be included in the reaction bath, and furthercross-linking obtained by impregnation with benzoyl peroxide or otherorganic peroxy compounds followed by baking or irradiation withultraviolet light.

Fabrics of the type described herein having what is known as one-way ortwo-way stretch are useful in a number of applications. For instance,they may be incorporated into clothing such as girdles, brassieres, andother undergarments, bathing suits, hat bands, stocking tops,

elastic bandages, athletic supporters, trusses, etc. For these and otheruses a variety of constructions and fabrics of different weights anddegrees of elasticity are required. By control of the extent oftreatment the elastic emciency and the elastic modulus may be variedover wide limits, thus meeting these requirements.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A process for obtaining elastic fabrics which comprises treating at atemperature of from 50 C. to C. a textile fabric composed of fiberscomprising filaments of synthetic linear polyamide containinghydrogen-bearing amide groups and capable of being cold drawn at least300% with a reaction solution having a pH below 3 containing not morethan 20% water and comprising formaldehyde, an aliphatic alcohol and anoxygen containing acid catalyst, continuing the reaction until dwellingof said polyamide filaments takes place and until the alkoxymethyisubstitution of the hydrogen of the amide groups is from 35% to 55%, anddiscontinuing the reaction before any substantial solution of saidfilaments takes place, said alcohol being selected from the groupconsisting of primary and secondary alcohols.

2. A process for obtaining elastic fabrics which comprises treating at atemperature of from 50 C. to 90 C. a textile fabric composed of fiberscomprising filaments of synthetic linear polyamide containinghydrogen-bearing amide groups and capable of being cold drawn at least300% with a reaction solution having a pH below 3, containing not morethan 20% water and comprising formaldehyde, an aliphatic alcohol and anoxygen containing acid catalyst, continuing the reaction until swellingof said polyamide filaments takes place and until the alkoxymethylsubstitution of the hydrogen of the amide groups is from 35% to 55%,and, before any substantial solution of said filaments takes place,stopping the reaction by immersing the filaments in an alcohol, andthen, after partial extraction of the reactants, immersing the filamentsin water.

3. A process for obtaining elastic fabrics which comprises treating, ata temperature of from 50 C. to 90 C. with a reaction solution having apH below 3 containing not more than 20% water and comprisingformaldehyde, an aliphatic alcohol and an oxygen containing acidcatalyst, a textile fabric woven in one of the warp and fillerdirections with fibers non-reactive with said solution and woven in theother of said directions with filaments of synthetic linear polyamidecontaining hydrogen-bearing amide groups and capable of being cold drawnat least 300%, continuing the reaction of said solution on the polyamidefilaments until swelling thereof takes place and until the alkoxymethylsubstitution of the hydrogen of the amide groups is from 35% to 55%, anddiscontinuing the reaction before any substantial solution of saidfilaments takes place, said alcohol being selected from the groupconsisting of primary and secondary alcohols.

4. A process for obtaining elastic fabrics which comprises treating, ata temperature of from 50 C. to 90 C. with a reaction solution having apH below 3 containing not more than 20% water and comprisingformaldehyde, an aliphatic alcohol, and an oxygen containing acidcatalyst, a textile fabric woven in both the warp and filler directionswith filaments of synthetic linear polyamide containing hydrogen-bearingamide groups and capable of being cold drawn by at least 300%,continuing the reaction of said solution until swelling of the polyamidefilaments takes place and until the alkoxymethyl substitution of thehydrogen or the amide groups is from 35% to 55%. and discontinuing thereaction before any substantial solution of said filaments takes place,said alcohol being selected from the group consisting of primary andsecondary alcohols.

5. The process set forth in claim 1 in which said filaments areessentially wholly undrawn.

6. The process set forth in claim 1 in which said alcohol is one havingnot more than four carbon atoms.

7. The process set forth in claim 1 in which said reaction solution isessentially non-aqueous.

8. The process set forth in claim 1 in which said polyamide ishexamethylene adipamide.

9. The process set forth in claim 1 in which said filaments areessentially wholly undrawn, in which said alcohol is one having not morethan four carbon atoms, and in which said reaction solution isessentially anhydrous.

10. The process set forth in claim 1 in which 10 which they arenon-reactive with said solution.

ALLAN K. SCHNEIDER.

REFERENCES CITED The following references are of record in the 15 fileor this patent:

UNITED STATES PATENTS Number Certificate of Correction Patent No.2,441,085.

Name Date 2,177,637 Coflman (l) Oct. 31, 1939 20 2,275,008 Colman (2)Mar. 8, 1942 FOREIGN PATENTS Number Country Date 565,066 Great BritainOct. 25. 1944 May 4, 1948.

ALLAN K. SCHNEIDER It is hereby certified that error appears in theprinted specification of the above numbered patent re uiring correctionas follows: Column 8, line 20, for the word "dwelling read swel my; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the case 1n the Patent Signedand sealed this 29th day of June, A. D. 1948.

THOMAS F. MURPHY,

Assistant (Zommz'ssioner 0 f Patents.

least 300%, continuing the reaction of said solution until swelling ofthe polyamide filaments takes place and until the alkoxymethylsubstitution of the hydrogen or the amide groups is from 35% to 55%. anddiscontinuing the reaction before any substantial solution of saidfilaments takes place, said alcohol being selected from the groupconsisting of primary and secondary alcohols.

5. The process set forth in claim 1 in which said filaments areessentially wholly undrawn.

6. The process set forth in claim 1 in which said alcohol is one havingnot more than four carbon atoms.

7. The process set forth in claim 1 in which said reaction solution isessentially non-aqueous.

8. The process set forth in claim 1 in which said polyamide ishexamethylene adipamide.

9. The process set forth in claim 1 in which said filaments areessentially wholly undrawn, in which said alcohol is one having not morethan four carbon atoms, and in which said reaction solution isessentially anhydrous.

10. The process set forth in claim 1 in which 10 which they arenon-reactive with said solution.

ALLAN K. SCHNEIDER.

REFERENCES CITED The following references are of record in the 15 fileor this patent:

UNITED STATES PATENTS Number Certificate of Correction Patent No.2,441,085.

Name Date 2,177,637 Coflman (l) Oct. 31, 1939 20 2,275,008 Colman (2)Mar. 8, 1942 FOREIGN PATENTS Number Country Date 565,066 Great BritainOct. 25. 1944 May 4, 1948.

ALLAN K. SCHNEIDER It is hereby certified that error appears in theprinted specification of the above numbered patent re uiring correctionas follows: Column 8, line 20, for the word "dwelling read swel my; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the case 1n the Patent Signedand sealed this 29th day of June, A. D. 1948.

THOMAS F. MURPHY,

Assistant (Zommz'ssioner 0 f Patents.

